flathead engine temps?

D

derek costello

Senior Member
I have a rebuilt '52merc with 60thou rebore and stock heads, dual 94s, pcv....
new alum rad, 16" electric fan..............but..........

with the engine running for 20 minutes the gage says 190f the oil press says
60psi.. The coolent level is about 1/2" above the rad core.

When I shoot the infrared temp meter at the top hoses it reads 167f ?
When I shoot the bottom hoses it reads 185f ?

If the water flow is down through the rad, shouldn't it be cooler at the bottom hoses ? The engine doesn't overheat and these readings seem constant.

Am I thinking that the flow is backwards or just stupid??
 
Very interesting, First at what rpm is the 60lb oil pressure, seems very high. Yea I agree with you the upper radiator hoses should be at the hi temp. I like to run my engines between 180/200 for best economy and longevity
 
Don't shoot the hoses. Shoot the radiator right under where the top hoses connect, and at the radiator just above the hose connection. That should show a temp drop af maybe 20 degrees.
 
My rpm was at 1000 for the 60psi, it drops to 45lbs at 500rpm idle. I shot the hoses and the rad tanks and the readings were the same??? I always thought that if things were normal
you should see a drop of 20degrees from the top to the bottom of the rad with the fan working properly! But not the other way round....any other thoughts??
 
I would take the temp reading at the exit of the head where the radiator hose connects, the metal, not the hose itself. And the other reading at the inlet to the water pumps, again, the metal, not the hose itself.
 
You are right so I did take the temp readings at the thermostat housing and at the water pump inlet castings, and those I my posted results???

I think maybe I have reversed water pumps (just kidding). but that is what it seems like,
I have never seen an engine with temps higher at the bottom of the rad???
 
derek costello said:
You are right so I did take the temp readings at the thermostat housing and at the water pump inlet castings, and those I my posted results???

I think maybe I have reversed water pumps (just kidding). but that is what it seems like,
I have never seen an engine with temps higher at the bottom of the rad???
Click to expand...


YES in all the old Fords the HOT water is moved out the bottom hose
connections up through the radiator into the top tank. From the top tank
through the top hoses and back into the engine. G.M.
 
G.M. said:
YES in all the old Fords the HOT water is moved out the bottom hose

connections up through the radiator into the top tank. From the top tank

through the top hoses and back into the engine. G.M.
Click to expand...

What!!!
I AM SKEPTICAL THAT IT'S TRUE.
That means it wouldn't be able to pump water if it was low on coolant at all.
 
Last edited:
When I had similar issues while checking my flathead I found that I needed to move the infrared gun further away from the ignition wires. I was getting electrical interference that was skewing the numbers. Also, the guns work better on a non-reflective surface. You can use duct tape / painters tape for target areas.
 
Dan in MI said:
When I had similar issues while checking my flathead I found that I needed to move the infrared gun further away from the ignition wires. I was getting electrical interference that was skewing the numbers. Also, the guns work better on a non-reflective surface. You can use duct tape / painters tape for target areas.
Click to expand...

Something along these lines have to be going on, don't think the radiator is heating up the coolant! :)
 
Take those temp readings after you drive it on the road. Are your lower hoses somehow restricting flow?
 
G.M. said:
YES in all the old Fords the HOT water is moved out the bottom hose
connections up through the radiator into the top tank. From the top tank
through the top hoses and back into the engine. G.M.
Click to expand...

I don't get it. This statement contradicts many threads on here.
 
Will D: Excellent point. "Going with the flow" as described is incorrect.

Perhaps that was a test to see who's paying attention. To pass the test just watch the water flow with the radiator cap removed.
 
Even if you rotated the pump pulleys the reverse direction they would still pull water from the center of the pump (bottom of the radiator) and push it out the top of the heads.

The problem here is most certainly the instrument being used to measure the temperature, or how it is being used.
 
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